This invention relates to electric motors, and more particularly to a DC motor of the type having a rotor provided with a commutator and a stator provided with brushes and supply terminals, and having an air gap contrived between the stator and the rotor.
Some motors of this type belong to a category in which one of the two parts, either the rotor or the stator, is provided with permanent magnets. Such motors are generally called electromechanical transducers. This is understood to mean a category of small, fractional horsepower motors used mainly in measuring, regulating, or control installations, or as sensing elements. The supply voltage is usually relatively low, and the windings are often made up of very fine insulated wires.
A number of difficulties are encountered in the manufacture of such motors owing to the small size of the various elements to be assembled, and especially to the fineness of the winding wires. The ends of these wires must frequently be connected to wires of larger diameter constituting the current leads connecting the windings to the input terminals. Other difficulties are involved in the positioning of the coils and in mounting them in such a way that the air gap is as narrow as possible.
Furthermore, a distinction is made between commutator motors in which the rotor bears coils and motors in which the coils are fixed, the rotor is provided with permanent magnets, and the current reversal is controlled by electronic means comprising detectors of the orientation of the rotor.
In the category of motors with permanent magnet rotors, it is known to be possible to use substrates bearing patterns of printed conductors for performing certain functions, especially the connection of the stator coils to the supply terminals, or the measurement of the speed of rotation of the rotor (cf. German Laid-Open Application No. 26 47675, Japanese Laid-Open Application No. 58-3558, and French Pat. No. 2,369,728).